Microwave electrodes for medical therapy



P 8, 1 970 K. FRITZ MICROWAVE ELECTRODES FOR MEDICAL THERAPY Filed Sept.19. 1966 2 Sheets-Sheet 1 INVENTOR:

Sept. 8, 1970 K. FRITZ MICROWAVE ELECTRODES FOR MEDICAL THERAPY FiledSept. 19. 1966 2 Sheets-Sheet 2 Fig.7

United States Patent 3,527,227 MICROWAVE ELECTRODES FOR MEDICAL THERAPYKarl Fritz, 26 Wendelsteinstr., 6200 Wiesbaden- Dotzheim, Germany FiledSept. 19, 1966, Ser. No. 580,534

Claims priority, application Germany, Sept. 17, 1965,

F 47,222; Jan. 10, 1966, F 48,121; Feb. 28, 1966,

Int. Cl. A61n /00; H05b 9/06 US. Cl. 128-410 3 Claims ABSTRACT OF THEDISCLOSURE A radiator element, for example in form of a pair ofconcentric cylinders, a cylinder with a wire therein, is formed suchthat a slot effect is obtained; the slot is dimentioned and arranged tobe out of resonance with a supply frequency, so that radiation from oneslot region will be superimposed upon the radiation of another slotregion, to provide a radiation pattern in a well defined region of thebody, to which the radiator element is applied.

The present invention relates to electrodes, or antennas to radiatemicrowave energy for use in microwave therapy.

The electrodes, according to the present invention, consist of anenvelope, or casing of conductive material which is formed withradiating slots. Radiation is emitted to the outside of the envelopethrough the slots, and can be beamed to a desired direction, for exampletowards a desired part of the human body, or to other objects to betreated, or irradiated with microwaves. The electrodes according to theinvention enable the application of microwaves in the medical fieldbecause they permit the application of microwaves in various specificbeam patterns to a well defined spot to be treated, so that no energy islost, and stray energy can be avoided. Thus, a supply of microwaveenergy at about 10 watts, requiring apparatus which in the aggregateweights only about 1 /2 kg. is feasible, although equipment having anequal effect, and not being capable of presenting microwave energy inwell defined regions may require total energy of from 100 to 150 watts,involving equipment weight of upwards of 12 kg.

It is an object of the present invention to provide antenna radiatorsfor microwave frequency energy which are efiicient, capable of directingenergy in a predetermined pattern and location, and additionally ofsufficient small size'and light weight to be useful in medicalapplications.

Briefly, in accordance with the present invention, radiating slots orslot regions of special form and configuration are provided in antennaelements and dimensioned such that they are radiating out of phase, andout of frequency with respect to each other but in such a manner thatthe radiation from any one of the slots will add to that of any other,so that the total radiation diagram, representing the radiation effectas a whole will be as desired. The radiator element itself may havevarious forms; for example, a ring-shaped slot radiator with circularpolarization may be provided, having a minimum of radiation in the axialdirection which, when properly shielded, can be used to irradiate thesinus cavities surrounding the eye, leaving the eye however free ofradiation.

Radiating slots, as such, are known and have been used heretofore withdimensions arranged to resonate at the frequency to be used. The narrowradiating slots, according to the present invention, are not inresonance with the radiation and produce a combined radiation patternwhich, when viewed from a point outside of the radiation chamber, willbe a composite of the radiation from each one of the slots, each oneemitting radiation in a certain direction with a certain polarity, at acertain amplitude and phase. When a number of such slots are used, whichhave different directions of radiation, the effects of radiation ofthese slots with respect to the point outside of the chamber will add,so that a total radiation diagram representing the effect of theradiator as a whole can be obtained.

The structure, organization and operation of the invention will now bedescribed more specifically in the following detailed description withreference to the accompanying drawings, in which:

FIG. 1 is a longitudinal, cross sectional view through a circularelectrode in accordance with the present invention;

FIG. 2 is a side view of the electrode of FIG. 1, illustrating amodification;

FIG. 3 is a plan view of the electrode of FIG. 1;

FIG. 4 is a sectional, perspective view of a circular electrodeillustrating another embodiment;

FIG. 5 is a schematic plan view of another embodiment;

FIG. 6 is a partly perspective, partly schematic view of anotherembodiment; and

FIG. 7 is a plan view of the electrode of FIG. 6, and indicating aradiation pattern.

Referring now to the drawings, and more particularly to FIGS. 1 and 2:electrodes 1', 1", cylindrical in shape, are separated by a gap forminga slot at the upper end in FIG. 1, and are closed, at the bottom, toprovide a cavity in the form of a .cylindrical ring therebetween. Theeffective axial length of the cavity is M4; the effective length isequal to the axial length, when the gap is an air gap, but may bereduced if the cavity is filled with a dielectric material. The upperopened rim of the cavity is curved to fit the contour of the objectwhich is to be irradiated. FIG. 1 illustrates a curvature to fit overthe human eye. The cavity has an outer metallic wall 1", with an upperopen slot. A ring-like extension 2 (FIG.

ice

1) is provided to bear against the human body; extension 2' may becovered with an elastic covering 4, such as soft rubber or foamedplastic. A representative radiation diagram is indicated by dotted linesR; the radiation, as appears from the diagram, is in form of a ring,with no radiation emanating from the center. Excitation power to obtainthe radiation is applied by connection to a coaxial cable at point C, aswell known in the art. The polarization of the radiation will becircular. As each dipole element of the slot has a corresponding dipoleelement oscillating with the same amplitude, but opposite in phase,radiation along the central axis is a minimum. This minimum may,however, be distributed by reflections at the surface of the body towhich the electrode is applied; if the eye is deeply set into the head,residual radiation may fall thereon. A second resonance chamber 3 formedby inner wall 1' of the main resonance chamber 1, and by a furthercylindrical metallic element 3 is coupled, by such residual radiation,to oscillate in a phase which will broaden and deepen the radiationdiagram R, and effectively remove any axial components of radiation.FIG. 2 illustrates a slightly different version of the electrode of FIG.1, and an improvement, in that within the inner cylinder 3 is shown anelongated element 5, slidable within cylindrical wall 3'. Spacing fromthe cylindrical wall can be obtained by small dielectric elements, notshown, as well known in the art. The upper rim of wall 1', curved to fitthe eye, is shown at 2. The lower rim, illustrated at 2", is curved toconform to the contour of the upper rim 2 so that the axial length ofthe cavity between wall 1 and wall 1" is maintained. Element (FIG. 2)additionally shields the eyeball from radiation.

The whole electrode may be made from aluminum,

galvanized plastic or the like, and may be arranged with a handle to behand-held and to be pressed against the region to be irradiated, forexample against the head of a patient around the eye, by compression ofresilient ring 2", so that the eye may be opened freely. Since the lowerend of the electrode unit may be open, that is only the cavity boundedby walls 1', 1 need be closed as shown at In (FIG. 1), the eye may beopened freely and the patient can look beyond the electrode. This pointis of particular importance for the feeling of safety and security ofthe patient. It is also possible to fasten or secure the radiatingelectrode to a special belt or holding element, so that it can besecured to the head if radiation is to extend for an appreciable periodof time.

FIG .4 illustrates another form of an electrode having a circular slot,to produce circular and linearly polarized radiation. This electrodecontains a central supply wire 6, to be connected to a coaxial cable asknown in the art. Wire 6 is connected to a radiation wire 8, of approximately circular outline, located within a cavity 7 which is cup-shaped,and forming a reflector. The circumferential length of wire 8 ispreferably 2X)\/ 2; ring 8 is connected by means of a mechanicallystrong wire 9, extend ing downwardly into the cup and then in ahalf-turn around the circumference to a radial spoke wire 10 and then tocentral conductor 6, as shown in FIG. 4. The wire 9, and the metallicwall together form an unsymmetrical Lecher system, having a fixed waveresistance. Wire 10 has a length of M4, and a coaxial cable formed ofthe metal extension of cup 7 and wire 6 has preferably the sameresistance.

The system of FIG. 4 is adapted to radiate with two components, namelywith two M2 dipoles, connected in parallel with a linear 'vector sum inlinear polarization, and also at the same time as a homogeneous loadedring in a ring-shaped field. The ring-shaped field exists between thewall and the antenna ring and is circularly polarized with a minimum ofradiation in the central axis, similar to the embodiment of FIGS. 1 and2. The edge of electrode 7 again may be padded, for example by means offoamed rubber 7 which may also be formed to extend across the entireelectrode to seal the element against dirt or contamination, and asschematically indicated in FIG. 4.

The electrode wire 8 of FIG. 4 need not be circular; referring to FIG.5, approximately the same amplitude of radiation for both circular andlinear polarization can be obtained when the ring has preferably anelliptical shape, and connected to the central conductor 9 at a pointabout 45 with respect to the larger axis of the ellipse. Such a wire 8',connected at point 9, and the geometric relationship of the wire to theelectrode cup 7 is illustrated in FIG. 5.

FIG. 6 illustrates another embodiment of an electrode in cup shape,utilizing similar principles as shown in FIG. 4. It permits a largerfield to be applied to the human body, and thus can result in a largerarea over which the blood circulation is to be improved by radiation.The total energy to be used will be the same as that in the electrode ofFIG. 4. Referring now to FIG. 6, the radiating electrode, or antenna,contains a ring 12 twice the length of the ring 8 in FIG. 4, that is alength of four \/2. By inserting small circumferential discontinuities,in the form of re-entrant, U-shaped bends 11, ring 12 can cover asurface three times as large as the electrode of FIG. 4 having ring 8therein. The wave length to be used with such an electrode can be about12 cm. (S-band). The individual portions of this ring radiator areoscillating in phase opposition, due to the double wave .length wire;the radiation,-thus, will be practically zero at any appreciabledistance from the electrode, while close to the electrode, the radiationwill have four distinct maxima 13, as schematically illustrated in FIG.7. The total energy of radiation, although the same as that of theelectrode of FIG. 4, is now concentrated at the four spots 13. As aresult of the paths of nerves, muscles, and blood vessels in the humanbody, which extend in many various directions, and are interlaced, thehuman body does not react to the four maxima, spots 13, separately, butrather reacts by a general rise of temperature in the entire regioncovered by electrode cup 7. Blood cicnla tion is therefore increasedover a larger area, the reaction of the body being as if the energysupplied would be three times as much as that of the energy of theelectrode of FIG. 4; of course, the penetration of the energy will beshallow. Such shallow penetration is sufficient for most therapeuticuse. The electrode permits application of microwave energy at minimumpower level. Both the electrodes of FIG. 4 and FIG. 6 may be covered bya plastic, or other suitable material 7 for ease of cleaning; in thealternative, paper or other disposable covers may be used. A conicalhandle, schematically illustrated in FIG. 4, may be arranged. A suitableimpedance matching element 14, shown in FIG. 6, may be incorporated insuch a handle.

What is claimed is:

1. Therapeutic device to apply radiation to a human body comprising aradiator element formed by a cylindrical body open at one side, and cupshaped;

a wire having a circular portion located within said cylindricalelement, closely spaced from the wall therefrom, so that a gap is formedbetween said cylindrical element and said wire; and

means supplying microwave energy at a predetermined frequency to saidcylindrical element and said wire, said gap forming radiating slotregions dimensioned and arranged with respect to the microwave energysupplied to be out of resonance therewith to provide a defined radiationpattern at a desired region of the body.

2. Device as claimed in claim; 1 wherein said wire, along itscircumference, is formed with re-entrant bends to providecircumferential discontinuities, the total length of the wire at itscircumferential direction being about twice the wave length at saidpredetermined frequency.

3. Device according to claim 1 wherein the wire within said cylindricalcup-shaped element is elliptical, said elliptical wire being connectedto said supply of microwave frequency at a point angled 45 with respectto the longitudinal axis of the ellipse, whereby the electrode willradiate with linear and circular polarization.

References Cited UNITED STATES PATENTS 6/1951 De Rosa et al. 343-789 10/1957 Haagensen 343-895 10/ 196-2 'Potzl 1128-422 7/1967 Kendall 12842211/ 1948 Buchwalter et al 343-771 1/1949' Hansen et a1. 343771 5/ 1957Lindenbald 343769 11/1965 Berry 343-770 10 1967 Jones 343771 ELILIEBERMAN, Primary Examiner US. Cl. X.R.

